Internal combustion engine oil pans are provided with threaded drain plugs whereby engine oil may be drained from the oil pan. However, repeated removal and insertion of the threaded drain plugs sometimes results in the threads in the oil pan being damaged to the extent that the threaded plug may no longer form a fluid-tight closure for the oil pan drain bore. Accordingly, various forms of replacement plug assemblies previously have been provided.
Some of these replacement plug assemblies include lengthwise stretchable, and thus radially contractable, resilient plugs, self-threading plugs and plastic plugs, or plug members configured for slidable lengthwise retraction from the sleeve bore. However, these previously known forms of replacement plugs are either difficult to remove when an oil change becomes necessary, require special tools for removal and/or insertion and are themselves limited in effective life span. Accordingly, a need exists for an improved form of replacement oil pan plug which may be repeatedly removed with ease and enjoy an extended expected lifetime of effective operation.
Various forms of plugs, couplings and other structures including some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 2,824,945, 2,935,338, 3,097,867, 3,229,069, 3,422,390, 3,423,110, 3,761,117 and 4,205,758. However, these previously known structures are believed to fail to provide an effective readily removable and repeatedly usable replacement oil pan plug, or describe a structure that can be improved.